Monday, June 3, 2013

Traffic Engineering Bashing - Justified or Not?

This started out as a simple reply on an ITE listserv, but became a blogpost. The discussion centered on traffic engineers being left out of conversations. My thoughts are this:

I used to be defensive about traffic engineering bashing. I would argue and try to dispell the myths. I would think that we're now transportation engineers (not just focused on traffic). It was something that bothered me a bit early in my career.

I found as I worked in many different communities across the country in the private sector that traffic engineers were mostly focused on our own bias and experience. For most of the U.S. this is largely vehicle focused. Most of us drive our cars every day. Some a whole lot further than others. Those that drive a long ways seem to be even more clear on an objective of reducing delays for people in vehicles. This was a challenge for a consultant working for a transit agency trying to implement signal priority.

One of the things I have learned in my career is that it is important to be self aware. Personal bias is part of our problem for our industry. We're often defenders of mobility because that's been our metric. Safety hasn't been as clearly defined, there is a lot of gray area in  what constitutes safe conditions.

My experience in the public sector has provided me with another perspective on this that I think is helpful to the community. After working in an agency that is focused on multimodal solutions, it is clear that we (engineers) often have a choice to be part of the solution as opposed to the problem. We are often at our best as problem solvers, working with the community as opposed to telling the community what they can or can't do. Obviously, there are limits, but I have experienced many cases where we tell our fellow professionals what we see as the problem. A better approach is to consider the overarching policy of the agency, the context of the situation, and the unique conditions of the particular community you're working in before we describe the solution. Doing this without personal bias is difficult, but I think that's our job.

In Portland, multimodal safety and neighborhood livability are our main objectives. Our official mission statement is: The City of Portland Bureau of Transportation is a community partner in shaping a livable city. We plan, build, manage and maintain an effective and safe transportation system that provides people and businesses access and mobility. We keep Portland moving.

To go from big picture to details, let me use a signals example. The Flashing Yellow Arrow for left turn operations is a great example of this. It's a tool that could be used to move people more efficiently. So why doesn't the City implement them as a standard?

Years of research (I worked on this as a graduate student) identified the FYA as a new display that would reduce the potential for yellow trap and improve clarity of information to drivers. It also benefits people to reduce delays. The new problem that was created as compared to protected only was that we introduced a condition where left turning vehicles had to yield to pedestrians and people on bicycles. It's not an issue of the Flashing Yellow (the same occurs with a doghouse circular green), but it confirmed what most of us already know: permissive left turns introduce a level of risk from a safety standpoint. Permissive left turns are not inherently bad unless there is a lot of exposure potential and high risk.

One of the challenges of our engineering curriculum is that we have been taught that failure is something to be avoided. Using the Highway Capacity Manual, failure is 80 seconds per vehicle. The problem with this is that in some communities (this may not be yours) the delay should be considered for people and not just vehicles. In downtown settings, there is an interest in prioritizing access for transit or pedestrians and the 80 seconds per vehicle threshold is not the best metric to use to determine effectiveness of a signalized intersection.

My experience in Portland is slightly different than Pete Yauch's in Florida. We get complaints about pedestrian delay and observations from bus operators in addition to folks that are sitting in their cars. Our policies make us put the community first. We want to keep people moving, but safety is our highest goal, so we're balancing those. We have flashing yellow arrows installed cautiously in the City where the safety risk is low for multimodal crashes. We are revisiting the Level of Service standards that put vehicle traffic as the primary measure used to determine adequacy of the transportation system by considering transit and the experience of additional modes. We are looking for ways to reduce costs to our customers, because that's just good government. It is important that we do a better job of prioritizing freight where possible to improve our economic competitiveness. We are context sensitive, solutions orieinted, and focused on serving the citizens.


Colin Swales said...

Peter, do you have a link to your presentation "Confessions of a Traffic Engineer: The Misuse of Level of Service and its Impact on Active Transportation" ?

Colin Swales, Ashland, OR

Calamityville said...

There are several things that can be done to mitigate the danger to pedestrians and bicyclists at a flashing yellow arrow as you know, including activating the main street pedestrian movements. Portland employs one of the more sophisticated controller software packages currently available and it includes many features designed specifically for the FYA.

One of my frustrations as someone who did a lot in my transportation career to facilitate pedestrians and bicyclists is that the FYA is a relatively easy way to accommodate both cars and bicyclists turning left. It can be done safely. It doesn't need to be the standard, but it's a tool in the tool box that's currently under utilized in Portland.